The present invention relates generally to brushes and the art of brush making, and more specifically, to a bristle sub-assembly in which bristles are connected at a base end to a supporting xe2x80x9cbeam,xe2x80x9d which could take the form of a base string, a bond line, or other structure which joins the common base ends of the bristles together in a row. A particularly useful application of such bristle sub-assemblies is in brush structures where segments of bristle sub-assemblies span open areas of a brush head or other supporting structures, and the flexibility of such bristles is at least in part determined by torsional characteristics of the beam.
The aforementioned co-pending applications describe a method of making bristle sub-assemblies which involve wrapping a polymeric monofilament around a mandrel and bonding the individual wraps to one or more base strings by applying thermal energy. According to the aforementioned applications, an apparatus for making bristle sub-assemblies includes a rectangular-shaped mandrel around which is wrapped at least one continuous strand or monofilament. The strands or monofilaments form a plurality of xe2x80x9cwrapsxe2x80x9d which are then placed in contact with at least one xe2x80x9cbase string,xe2x80x9d which runs generally orthogonally to the wraps. At the points of contact between the wraps and the base strings, ultrasonic energy is applied to cause the individual wraps and base strings to bond together. At a downstream processing point, cutters are used to turn the bonded base strings and wraps into bristle sub-assemblies.
One particularly preferred apparatus for making bristle sub-assemblies is shown in FIG. 1, wherein the apparatus 10 includes a rectangularly shaped mandrel 12, around which is wrapped a monofilament 14. A wrapping mechanism 16 rotates around the mandrel 12, laying out a plurality of xe2x80x9cwrapsxe2x80x9d 18, which are moved vertically along the mandrel 12 by a conveyer mechanism, generally referred to by the numeral 20.
Four base strings 22 are fed into contact with the wraps from supply sources (not shown) near respective heating elements 24. When energy is supplied to the ultrasonic heating elements in contact with the base string, the surfaces of the monofilament wraps and/or the base strings, which are in contact with each other, become plastic; after cooling, which occurs immediately after the wraps move away from the heating elements, the wraps of monofilament and the base strings become bonded together.
As the bonded wraps and base strings move further away from the heating elements, they pass through cutters 26, only two of four being seen from the view of FIG. 1. The cutters 26 slit the bonded wraps into four bristle strings 28, each of which can be taken up on reels (not shown) or other means for further processing.
FIG. 2 is an enlarged view showing the point of contact of one of the monofilament wraps 18 and one of the base strings 22. The base string is held by a horn 30 of the ultrasonic heating element, while a cable 32 of the conveyor mechanism 20 translates the monofilament wraps up the mandrel 12. The cable 32 and base string move in the same direction at the same speed, so that the bonded wraps and base string are moved to the cutters 26 and spit into separate bristle strings 28.
One of the bristle strings 28 is shown in FIG. 3, as having a base string 22, and two rows 34 and 36 of bristles which are made of the monofilament that had previously been used to form the wraps. The bristle rows have a tendency to form a V-shape, with the base string at the vertex of the xe2x80x9cV.xe2x80x9d Further processing steps can be used to render the rows of bristles parallel to each other; alternative orientations can also be made when desired.
The details of how the bristle strings are formed, and how they can be combined with brush bodies to form a variety of brushes, are described in the aforementioned co-pending and related applications, which are incorporated herein by reference. In making brushes using the bristle strings described herein and in the related and co-pending applications, the bristle strings are cut into lengths that can be called xe2x80x9cbristle sub-assemblies.xe2x80x9d These lengths can be embedded in or otherwise attached to the brush bodies to form a wide variety of sizes, shapes and types of brushes.
While the bristle sub-assemblies described above have many advantages, a continuing need exists for improved brushes and bristles employed in same, as well as for methods and means for varying or otherwise controlling the stiffness of the bristles without necessarily changing the physical parameters of the bristles themselves.
An object of the present invention is to provide a bristle sub-assembly in which the stiffness of the bristles can be varied by changing one or more parameters of the beam structure that supports the bristles.
Another object of the invention is to provide a method of varying the stiffness of the bristles of a brush by changing one or more parameters of the beam structure used to support the bristles of the brush.
Still another object of the present invention is to provide a method of changing the stiffness of a bristle without changing the material or diameter of the bristles themselves.
These and other objects are met by providing a brush which includes a brush body, at least one bristle sub-assembly having a support beam having first and second opposite ends and a row of bristles having proximal and distal ends, at least one point of attachment between the brush body and the support beam, thereby defining at least a portion of the bristle sub-assembly that extends into free space, and means for varying the stiffness of the bristles of the bristle sub-assembly.
Preferably the means for varying the stiffness of the bristles is a physical parameter of the beam, such as cross-sectional shape, material properties Young""s Modulus, and thickness. Additional means for varying the stiffness include coating at least a lower portion of the bristles with a polymeric, preferably elastomeric, material, and altering the cross-section of the bristles, such as by tapering the end portions.
These and other objects and features of the invention will be better understood in referencing the following detailed description and drawings.